Social dynamics of core members in mixed-species bird flocks change across a gradient of foraging habitat quality

PLoS One. 2022 Feb 2;17(2):e0262385. doi: 10.1371/journal.pone.0262385. eCollection 2022.

Abstract

Social associations within mixed-species bird flocks can promote information flow about food availability and provide predator avoidance benefits. The relationship between flocking propensity, foraging habitat quality, and interspecific competition can be altered by human-induced habitat degradation. Here we take a close look at sociality within two ecologically important flock-leader (core) species, the Carolina chickadee (Poecile carolinensis) and tufted titmouse (Baeolophus bicolor), to better understand how degradation of foraging habitat quality affects mixed-species flocking dynamics. We compared interactions of free ranging wild birds across a gradient of foraging habitat quality in three managed forest remnants. Specifically, we examined aspects of the social network at each site, including network density, modularity, and species assortativity. Differences in the social networks between each end of our habitat gradient suggest that elevated levels of interspecific association are more valuable in the habitat with low quality foraging conditions. This conclusion is supported by two additional findings: First, foraging height for the subordinate Carolina chickadee relative to the tufted titmouse decreased with an increase in the number of satellite species in the most disturbed site but not in the other two sites. Second, the chickadee gargle call rate, an acoustic signal emitted during agonistic encounters between conspecifics, was relatively higher at the high-quality site. Collectively, these results suggest an increase in heterospecific associations increases the value of cross-species information flow in degraded habitats.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Ecosystem
  • Passeriformes / physiology*
  • Seasons
  • Social Behavior*
  • Songbirds / physiology*

Grants and funding

This work was supported by the National Science Foundation, Division of Integrative Organismal Systems (https://www.nsf.gov/div/index.jsp?div=IOS; [NSF1353326-ios, 2014 awarded to JRL; NSF1353308-ios, 2014 awarded to KES; and NSF1353327-ios, 2014 to TMF]). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.